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PBOCEEDLTSTGS of the geological society. 



[Nov. 21, 



with red sandstones, apparently identical with those on the other 

 side, but so dislocated as to present the appearance of the broken 

 half of an arch ; and a few yards further from the beach the beds are 

 brought to a vertical position ; and thus forming a fan-shaped con- 

 tortion, they commence dipping to the eastward at angles at first 

 veiy high, but becoming lower and lower as we proceed westward. 

 The relations and order of succession of these rocks are, however, 

 much better seen in fig. 5, showing a section of the Carboniferous 

 series, from Tiquina to La Guardia, in an east and west direc- 

 tion. This section appears to represent the entire thickness of this 

 formation. 



The above section will require no further explanation or descrip- 

 tion of succession ; but with reference to the fossils, I may state 

 that those which I was enabled to extract from these beds have been 

 named by Mr. Salter as follows : — 



Productus semireticulatus, Martin. Athyris subtilita, Hall. 



(P. Inca, D' Orb.) Orthis resupinata, Sow. ? 

 Productus Longispina, Sow. (Capacii, Andii, If Orb. 



along with numerous fragments of Corals and Crinoids in too imper- 

 fect a state to admit of being recognized. 



A Phacops, named in Plate IV. Phacops Pentlandii, was brought 

 from Aygatchi at the south end of the Lake of Titicaca, by Mr. 

 Pentland in 1838, and supposed by him to be in the Carboniferous 

 rocks there ; but, according to Mr. Salter, this is an Upper Devonian 

 type. It might possibly come from the sandstone series at the base 

 of the Carboniferous, as the rock in which the specimen is imbedded 

 seems to point out ; in such a case these sandstones may be of Upper 

 Devonian age. 



I have not had an opportunity of visiting the Carboniferous beds 

 in the provinces of Arque or Oruro ; from the former, Colonel Lloyd 

 some time ago sent home the following species : — Spirifer Condor, 

 S. lineattis, Productus Cora, P. Inca, P. Boliviensis, and Orihis Andii. 



The Carboniferous rocks of the Department of Santa Cruz appear 

 to form a perfectly distinct series from the above-described isolated 

 basins, being situated at a much less elevation above the sea, and cut 

 off from all connexion with the others by the intervening mountain- 

 chain of the Andes. According to M. D'Orbigny they are of much 

 greater extent ; and the fossils which I have seen appear in much 

 more perfect preservation. Mr. Gumming brought to England the 

 following fossils, stated to be from Santa Cruz : — Terebratula mille- 

 punctata, Rhynchonella Peruviana, R. Pleurodon, Spirifer Boliviensis, 

 and S. Condor. 



M. D'Orbigny has coloured on his map as Carboniferous a small 

 patch around and including the " Morro de Arica," which is seen in 

 Section No. 2 as a steep hill rising perpendicularly from the water's 

 edge to the height of about 500 feet above the sea. The evidence he 

 adduces is the occurrence of traces of a Productus in blocks of lime- 



D'Orb.) 

 Spirifer Condor, D'Orb. 

 Boliviensis, D' Orb. 



Rhynchonella (new species). 

 Euomphalus (Phanerotinus ?). 

 Bellerophon ; like B. Urii, Flem. 



